Popular smoking articles, such as cigarettes, may have a substantially cylindrical rod-shaped structure and may include a charge, roll or column of smokable material, such as shredded tobacco (e.g., in cut filler form), surrounded by a paper wrapper, thereby forming a so-called “smokable rod” or “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping material.” It also may be desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.
After use, the discarded portion of the cigarette is primarily composed of the filter element, which typically consists of tightly-compacted and highly crimped cellulose acetate fibers bonded at their contact points and wrapped by the plug wrap and tipping material. The presence of the wrapping materials, the fiber-to-fiber bonding, and the compacted nature of conventional filter elements has a detrimental effect on the rate of degradation of cigarette filters in the environment. Unless the filter element is unwrapped and the fibers spread apart to increase exposure, biodegradation of the filter can take several years.
Cellulose is a known biodegradable fiber which is capable of aerobic and/or anaerobic degradation in a variety of environments. However, cellulose has traditionally not been used for the production of fibrous tow for filter elements, due in large part to the poor taste of cigarette smoke associated with cellulose-based filter elements as compared with traditional cellulose-acetate-based filter elements. It is believed that the traditionally-used cellulose acetate is advantageous in providing acetate groups that can interact with and remove certain undesirable phenolic compounds from the vapor phase of cigarette smoke. Cellulose does not have acetate groups on the fiber surface and it is believed that this may contribute to the poor taste associated with cellulose-based filters. Surface acetylation of cellulose and other types of fibers to address this issue has been proposed. See, for example, U.S. Pat. No. 4,085,760 to Toyoshima. However, there is no commercial process available for surface acetylation, which generally requires long reaction times and/or toxic chemicals.
Certain filter elements for cigarettes have been developed which contain materials that may promote biodegradation of filter elements following use. For example, certain additives have been noted (e.g., water soluble cellulose materials, water soluble fiber bonding agents, starch particles, photoactive pigments, and/or phosphoric acid) which can be added to filter materials to enhance degradability. See, for example, U.S. Pat. No. 5,913,311 to Ito et al.; U.S. Pat. No. 5,947,126 to Wilson et al.; U.S. Pat. No. 5,970,988 to Buchanan et al.; and U.S. Pat. No. 6,571,802 to Yamashita; and US Pat. Appl. Publ. Nos. 2009/0151735 to Robertson and 2011/0036366 to Sebastian. In some cases, conventional cellulose acetate filter material has been replaced with other materials, such as moisture disintegrative sheet materials, extruded starch materials, or polyvinyl alcohol. See U.S. Pat. No. 5,709,227 to Arzonico et al; U.S. Pat. No. 5,911,224 to Berger; U.S. Pat. No. 6,062,228 to Loercks et al.; and U.S. Pat. No. 6,595,217 to Case et al. It has also been suggested that the incorporation of slits into a filter element may enhance biodegradability, as described in U.S. Pat. No. 5,947,126 to Wilson et al. and U.S. Pat. No. 7,435,208 to Garthaffner. Biodegradability has also been proposed to be imparted by use of certain adhesives, such as described in U.S. Pat. No. 5,453,144 to Kauffman et al. and US Pat. Appl. Publ. 2012/0000477 to Sebastian et al. Another possible means for enhancing biodegradability is replacing the conventional cellulose acetate filter material with a core of a fibrous or particulate cellulose material coated with a cellulose ester, as described in U.S. Pat. No. 6,344,349 to Asai et al.
Further advancements in filter elements and methods for producing the same are desirable. Particularly, additional methods for enhancing the biodegradability of filter elements for preparing such filters having enhanced biodegradability are desirable.